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In a Unity Momentum PLC, System Words %SW82 & %SW83 are not working correctly.

Goals and Symptoms

This resolution explains the System Words %SW82 and %SW83 in a Unity Momentum PLC.

Facts and Changes

The explanation of %SW82 and %SW83 in Unity Pro is incorrect. This is a Unity Help documentation issue.

Unity Pro V11 Help incorrectly states System Words %SW82 and %SW83 are used for Message Management in the M340, M580, Unity Momentum, Atrium, Premium, and Quantum ranges. Where,
%SW82 = Number of Modbus messages sent or received on serial port 1, updated at 1 second period.
%SW83 = Number of Modbus messages sent or received on serial port 2, updated at 1 second period.

These system words contain serial port counters for the Quantum range only.

Causes and Fixes

For the ranges M340, M580, and Unity Momentum, these system words are routing message counters.